So my model is small, like one block tall, obviously a cape at the normal position looks dumb on this model. So I did what I could to make it look less jarring and moved the cape position closer to my model. One small problem, whenever I start moving the cape starts floating behind my character instead of staying on their back...

Here are two screenshots, one where I'm standing still, and another where I'm moving.

It would appear no matter how or where the cape is moved it always returns to its default position when animating. This plays havoc on taller or shorter models which want to wear their capes at another height.